PROJECT SUMMARY Current head and neck cancer diagnosis and treatment planning suffers from poor spatial resolution of whole-body positron emission tomography (WB-PET) scans. In the neck, where tissue layers are thin, the spatial resolution of WB-PET (4-6 mm) is not sufficient to evaluate small lymph nodes (<5 mm), establish how far the tumor has invaded locally, and guide the decision to resect a tumor rather than irradiate and deliver chemotherapy. This proposal, responsive to PAR-18-009, ?Academic-Industrial Partnerships to Translate and Validate in vivo Cancer Imaging Systems,? seeks to address this problem by translating high resolution radiation detection technology to head and neck imaging. The project research team consists of researchers from the Department of Nuclear, Plasma, and Radiological Engineering at the University of Illinois at Urbana-Champaign and eV Products Inc., a world leader in semiconductors for radiation detection. To achieve its goal, this research will pursue the design, development, optimization, characterization, and validation of a dedicated head and neck PET scanner. The proposed system will be the first head and neck scanner to exhibit features as small as 1 mm with high photon sensitivity, enabled by the use of high energy and spatial resolution properties of cadmium zinc telluride (CZT) crystals. This system will be integrated into a transportable stage and is designed to not interfere with the conventional workflow of the WB- PET scan procedure, and has the additional attraction of being used for dynamic PET studies. We expect that this dedicated head and neck PET imaging system will deliver the following new capabilities: i) detection and evaluation of small lymph nodes, ii) improved treatment planning and determining the extent of the tumor growth, and iii) improved confidence in differentiating post-treatment change from tumor recurrence. The system will consist of two panels and have an adjustment for panel-to-panel separation distance. Each panel contains 150, 4x4x0.5 cm3 cross-strip CZT crystals covering a 20x15 cm2 panel area. The crystals will be mounted in an edge-on configuration for increased photon detection efficiency. A novel event recovery scheme based on the 3D position sensitive cross-strip crystals will be developed to recover multiple interaction photon events, reject random events, and significantly increase the photon sensitivity of the system. In the final year of the project, a study consisting of 20 patients will be conducted to evaluate the performance of the developed prototype and validate the potential benefits.